Eclipse ESCET website move eclipse.org to eclipse.dev

A while back, our website repo was moved (#415 (closed)). At that time, also the move of the website itself was announced, but it was withdrawn. See that issue for more information. Now, the move is back, but with some different details this time.

Basically, https://www.eclipse.org/escet will change to https://eclipse.dev/escet. Redirects from the former to the latter will be put in place. See eclipsefdn/helpdesk#3069 (closed) for the details.

Steps:

• Webmaster will take care of the actual move. The move will happen on July 4. If we want to do it earlier, we can let them know. We've asked to move sooner, see eclipsefdn/helpdesk#3091 (closed)
• It seems redirects will be added, including for deeper links. See eclipsefdn/helpdesk#3069 (closed). I assume this holds for http and https and with or without www, but I'm not sure. I asked a question about the www part. In any regard, we should test the redirects.
• We should update all links in our repo to the new canonical URLs. (!574 (merged))
• After all these changes, we may want to check the information about our project in the PMI, to see whether that all correctly reflects the new situation. There are some links there to the website as well.

I'm not sure I like the change. We've been telling everybody about our move to the Eclipse Foundation, including the URL to remember, and now they're changing it. But at least redirects are in place, so users should still arrive at the right place.